Veterinarians urged to remain vigilant
By Bridget M. Kuehn
Posted Aug. 1, 2004
The national Centers for Disease Control and Prevention has confirmed the first cases of rabies transmission through the donation of whole organs.
On June 30, the CDC confirmed diagnoses of rabies in three organ recipients and their common donor. On July 8, physicians at Baylor University Medical Center announced during a press conference that a fourth patient had died after receiving part of an artery from the infected donor and a liver from a separate donor.
These cases mark the first time the disease has been transmitted through the transplantation of solid organs, according to the CDC. Previously, eight cases of rabies transmission through transplanted corneas have been documented in five countries. At press time in July, field and diagnostic investigations were continuing. State health officials in Texas, Arkansas, Oklahoma, and Alabama were identifying and treating individuals who may be at risk of rabies exposure as a result of these cases.
Dr. Charles E. Rupprecht, the head of the rabies section at the CDC, said the case should remind veterinarians to be vigilant about rabies in cats and dogs, and aware that diseases can change over time.
"It shows that nature does teach old bugs new tricks," Dr. Rupprecht said.
Rabies transmission most often results from the bite of a rabid animal. Nonbite exposure through scratches, contamination of an open wound, or mucous membrane contact with saliva or neuronal tissue is rare, according to the CDC. In the cases of the three organ recipients confirmed by the CDC, the rabies virus was most likely transmitted through neuronal tissue in the transplanted organs, according to the CDC's Morbidity and Mortality Weekly Report for July 1. The CDC later confirmed the fourth case.
The organ donor was an Arkansas man who visited two Texas hospitals with severe mental status changes and a low-grade fever, according to the MMWR. Neurologic imaging revealed brain hemorrhaging that later caused the man's death. He was screened according to local organ donation regulations and passed. Rabies testing is not a part of routine organ donation screening.
The donor's lungs were transplanted into a person at an Alabama hospital who died of complications during the operation. The donor's liver and kidneys were transplanted into three recipients at Baylor University Medical Center on May 4. Between 21 and 27 days after the transplant, all three recipients developed neurologic symptoms, and later died.
Physicians from Baylor said that it is not uncommon for transplant recipients to experience neurologic symptoms as a result of blood flow problems, medication, or infection. But because the exact causes of death for the three recipients were not identified, specimens were sent to the CDC for diagnostic testing.
Testing by the CDC confirmed the rabies diagnoses, and found a strain of rabies common in bats that live in the area where the donor lived.
After receiving those results, officials at Baylor initiated an investigation to determine whether any other patients had received organs or tissues from the rabies infected donor, said Dr. William Sutker, the chief of infectious disease, during a press conference. Through that investigation, Baylor officials discovered that the fourth patient received a liver from another donor and part of an artery from the rabies-infected donor around the same time as the other three patients. Dr. Sutker said the patient died around the same time as the other patients.
Transmission of the rabies virus during an animal organ transplant is far less likely, Dr. Rupprecht said, because the organs come from a controlled population.
"It's the one situation where the control measures in veterinary medicine may be tighter than those in human medicine," he said.
Though it would be impossible to screen human organ donors for all possible diseases, officials from the CDC say the benefits of organ transplantation far outweigh the potential risks. Daniel Hayes, an organ transplant expert at the United Network for Organ Sharing, explained during a CDC teleconference that, though there are an estimated 40,000 cornea transplants in the United States each year, only one case of rabies transmission has been reported. Last year, there were more than 25,000 organ transplants and no reported cases of rabies transmission, he said.
"So, I don't think that such a rare event should trigger any kind of widespread panic or reaction to do testing for a disease that is so infrequent," Dr. Hayes said.
On average, there are one to three human cases of rabies in the United States each year, Dr. Rupprecht said. He attributes the low number of cases to the work of veterinarians, public health professionals, and professionals in emergency rooms, and to the biologics available.
These unusual human cases raise new questions about the pathogenesis of the disease, and highlight the need for veterinarians to research new and emerging diseases, Dr. Rupprecht said.
Dr. Rupprecht reiterated the need for all veterinarians to be vigilant about rabies, and unusual rabies cases.
"Veterinarians are going to be our eyes and ears because these things can happen in animals," he said.